This invention relates to a cool mug, particularly one having a close chamber filled with an absorptive polymer as a thermal storage substance for low temperatures so as to shorten time needed in freezing, and elongate frozen time as well.
A prior art cool mug shown in FIG. 1 is provided with two rims 10, 11, forming a closed chamber 12 in which water is held.
The cool mug 1 of the prior art is provided to keep drinks held therein cold and initially kept in a freezer so that the water filled in the closed chamber 12 becomes ice. However, the prior art cool mug 1 has been found to have the following disadvantages.
1. The low-temperature thermal storage substance, water needs four hours or so to be frozen in a common refrigerator.
2. The low-temperature thermal storage substance, water after frozen, quickly absorbs heat, defrosting in one hour or so.